Buffers typically are not the best way to raise alk or calk. A good 2 part additive would work well. I used to use B-Ionic. With a 2 part additive you add the same amount of both ingredients.
I now use Randy's 2 part number 1 formula, (number 1 formula because you bake the baking soda and thus it has a tendency to raise the ph) and limewater.
8.0 is fine for the ph. The question is how low does the ph go during the night? That is the other half of the equation you need to know. If you ph goes to 7.9 or so you are ok.
A critical factor is how do you measure the ph? If you are using test strips they are not accurate. If you are using a monitor that is good.
Calcium is another parameter you should also measure.
Calk, alk, ph and magnesium are the only ones I measure now.
Regards,
Pat
ps, the chemistry forum has many informative articles that will help.